Definition of "onerous"

That all this might not be too onerous on the purses of his rustic patrons, who are apt to consider the costs of schooling a grievous burden, and schoolmasters as mere drones, he had various ways of rendering himself both useful and agreeable.

1820, Washington Irving, The Legend of Sleepy Hollow

Again, and more intensely than ever, she desired a fixed occupation,—no matter how onerous, how irksome.

1849, Currer Bell [pseudonym; Charlotte Brontë], chapter 13, in Shirley. A Tale. […], volumes (please specify |volume=I to III), London: Smith, Elder and Co., […]

[I]t has become an onerous duty, a wearisome and distasteful task.

1910, Jack London, “The Golden Poppy”, in Revolution and Other Essays

The striker's job was onerous, too, because there was so little "give" in the metal, and the perpetual jarring was indeed trying to the muscles.

1945 January and February, A Former Pupil, “Some Memories of Crewe Works—III”, in Railway Magazine, page 13

However, given current sensibilities about individual privacy and data protection, the recording of oral data is becoming increasingly onerous for researchers[.]

2019, Li Huang, James Lambert, “Another Arrow for the Quiver: A New Methodology for Multilingual Researchers”, in Journal of Multilingual and Multicultural Development, page 11